Real-time in vivo radiation dosimetry using scintillation detector

ABSTRACT

Apparatus and methods for measuring radiation levels in vivo in real time. Apparatus and methods include a scintillating material coupled to a retention member.

The present application is a continuation application of U.S. Ser. No.13/143,567, filed Dec. 2, 2011, which is national phase applicationunder 35 U.S.C. §371 of international application Serial No.PCT/US2010/020366, filed Jan. 7, 2010, which claims benefit of priorityto U.S. provisional application Ser. No. 61/143,294, filed Jan. 8, 2009,the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the fields of radiationdosimetry. More particularly, it concerns the use of scintillatingdetectors to detect radiation levels in vivo.

2. Description of Related Art

Cancer recurrence is frequently the result of failed local control oftreatment options. Reducing the likelihood of recurrence in radiotherapymeans giving the largest possible radiation dose to the tumor regionwhile limiting the dose to healthy organs at risk for treatment-inducedtoxicity. Even with the best treatment planning modalities, there is noguarantee that the prescribed dose will be delivered exactly as planned.Internal movements such as breathing or uncertainties in the filling oforgans such as the bladder and rectum may displace the target volumeaway from the intended treatment field. At the same time, normal tissuesmay be shifted into the high dose region, introducing unnecessaryradiation-induced side effects. The use of in vivo dosimetry to monitorthe actual dose received in the target or healthy tissue is the best wayto ensure accurate dose delivery. Accurate in vivo dosimetry is animportant step towards measuring the dose to the organs at risk in orderto assess the quality of the treatment, maximize the dose to the tumorand/or minimize the risk of complications to normal tissues. Presentlythere are no known available in vivo dosimetry systems that can sampleboth dose and dose rate fast enough to be suitable for real-timefeedback.

With the advent of intensity modulated radiotherapy (IMRT) and conformalproton radiotherapy, there now exists the ability to create a treatmentplan with margins small enough to target the tumor while largely sparingthe healthy tissues and organs at risk. CT-Linac-based image-guidedradiotherapy (IGRT), cone-beam CT and on-board imaging (OBI) systemsallows a user to accurately set up a patient relative to the treatmentbeams just prior to treatment. However, there is no guarantee that thetarget will remain in the same place during the entire treatment period.Even with the use of increasingly sophisticated radiotherapy techniques,it is difficult to determine if the dose has been delivered exactly asplanned. And, if not, it can be difficult to determine the degree towhich the actual dose has deviated from the planned dose.

Precise measurement of the dose to organs at risk and other criticalstructures is therefore necessary to provide a clear picture of the truedose delivered during any given treatment fraction. The benefits of suchmeasurements are multi-fold. First, comparison of the measured dose tothat planned will indicate deviations in set up and/or anatomy thatindicate the need for changes in the treatment plan. Second,consideration of tumor control and the probability of normal tissuecomplications will allow a radiation oncologist to either escalate orreduce the dose over the course of a radiotherapy treatment. Finally,knowledge of the true delivered dose will allow for more accurateanalysis of organ toxicity. The benefits to the patients will includedecreased likelihood of local failure and reduced frequency oflife-altering side effects.

The main radiation dosimeters available at the present time includethermoluminescent detectors (TLDs), ionization chambers, radiographicfilm, silicon (Si) diodes and metal-oxide semiconductor field effecttransistor (MOSFET) devices. None of these detectors, aside from Sidiodes, allows real-time measurement of dose rate, and none are waterequivalent. TLDs, ionization chambers and film do not allow in vivo dosemeasurements for various reasons (too bulky, slow response, safetyconcerns, etc.). Even though Si diodes may have good spatial resolution,they suffer from strong energy dependence and are prone to doseperturbation depending on their orientation with respect to the beam(Beddar et al. 1994).

MOSFETs have been commercialized for in vivo dosimetry. Although somesystems offer unique advantages including the ability to be permanentlyimplanted and read telemetrically, MOSFETs tend to show angulardependence, energy dependence, and a decreased sensitivity withincreasing absorbed dose, requiring either in-house or factorycalibration (Soubra et al. 1994; Scarantino et al. 2004; Ramaseshan etal. 2004; Beddar et al. 2005). MOSFET detectors also have a limitedlifetime of 70-200 Gy.

Preliminary studies of optically stimulated luminescence (OSL) devicesdo show promise (Aznar et al. 2004; Aznar et al. 2005). The devicesproduce spontaneous emission due to radio-luminescence, which exhibits anon-linear dependence with dose rate, as well as optically stimulatedluminescence, which can be integrated to obtain the total accumulateddose.

Although these devices can be used for in vivo dose measurements, theysuffer from other drawbacks. These include their non-water-equivalenceand the required time delay of 5 to 6 minutes needed to retrieve thedose data between measurements. This occurs because the OSL signalrelated to absorbed dose arises from electron traps that must beoptically stimulated with a laser. Thus, one could not use thesedetectors to discriminate between individual beams in an IMRT or even atwo-field proton therapy treatment.

It is clear that none of the detectors described above would satisfy theneeds of the real-time in vivo dosimetry that would provide feedbackfast enough to enable adaptive radiotherapy. Only plastic scintillatorscan be used to measure both dose and dose rate in real time. Plasticscintillators have been shown to be water equivalent (Beddar, et. al1992), linear with dose, dose rate independent, energy independent inthe megavoltage energy range, and unaffected by changes in temperature.Moreover the light emission mechanism of a plastic scintillator is fast(nanoseconds) and therefore well suited for real-time applications. Sofar, several prototypes of plastic scintillation detectors have beenproposed for applications in quality assurance, stereotacticradiosurgery, brachytherapy and general dosimetry but no scintillationdetector to date can achieve real-time in vivo dosimetry.

A multiple-probe scintillation detector system has been recentlydeveloped for quality assurance but can only be used in phantom and notin patients. Moreover the design of this detector system requires anacquisition time that is at least as a long as a radiotherapy treatmentfraction, this design flaw prevents any real-time applications.

SUMMARY OF THE INVENTION

Delivering the correct dose to the intended area is the most basic goalof any radiotherapy treatment. The most direct way to confirm the truedose delivered to a location of interest is to measure that dose insitu. In prostate radiotherapy, the outcome (biochemical and localcontrol) depends on accurate delivery of the dose to the prostate asplanned. At the same time, it is important to ensure that the toleranceto critical structures (rectum, urethra, and erectile tissues) is withinacceptable limits so that toxicity is minimized and quality of life isnot compromised.

It is believed that direct measurement of the dose delivered to organs,critical structures, and within the vicinity of a tumor is feasible andcan be used to verify treatment plan delivery. It is also believed thatthis can be done using an in vivo scintillation detector composed ofmultiple probes arranged in an application-specific design that canmonitor true in vivo dose in real time.

Plastic scintillation detectors are constructed from three maincomponents: a miniature scintillating material that luminesces (emitsvisible light) when irradiated, an optical guide that carries the light,and a photodetector that converts the light into a measurable signal. Incertain embodiments, sub-millimeter diameter scintillating fibers willbe used for their spatial resolution as well as their flexibility,allowing them to conform to the curvatures of internal anatomy.

Objectives include the ability to: a) establish the dosimetriccharacteristics and properties of scintillating fibers in photon andproton radiotherapy beams as well as an lr-192 HDR brachytherapy source,b) design, construct, and test detector systems for rectal and urethralin vivo applications, and c) measure the dose to the rectal wall andurethra for a small cohort of patients.

Successful implementation of the disclosed systems and methods willallow for monitoring the true dose delivered to organs and other tissuesat risk during radiotherapy. This method can be used to generate data toassess the dose to the organs and critical structures and can be used tomaximize the dose to the tumor and/or minimize the risk of complicationsto normal tissue. The resulting data can also be used to studydose-related treatment side effects. The ultimate goal of utilizing thismethod is to improve the delivery of radiotherapy treatments and thequality of life of radiotherapy patients.

Certain embodiments of the present disclosure comprise an apparatusconfigured to measure radiation levels in vivo. In specific embodiments,the apparatus comprises: a retention member configured to retain theapparatus in a location in vivo; a scintillating material configured toemit light when irradiated; an optical guide configured to transportlight emitted from the scintillating material; and a photodetectorconfigured to detect light emitted from the scintillating material andtransported by the optical guide.

In particular embodiments, the retention member is inflatable. Theapparatus may further comprise a data analyzer configured to analyze anoutput from the photodetector. The scintillating material may beconfigured as an optical fiber in certain embodiments. The scintillatingmaterial may be coupled to the retention member in particularembodiments. The scintillating material may be wrapped around theretention member to form a spiral about a primary axis of the retentionmember to provide information about a radiation dose delivered to theall or part of the surface of the retention member. In otherembodiments, the scintillating material may be wrapped around theretention member to form an annular arrangement about a primary axis ofthe retention member. In certain embodiments, the scintillating materialis arranged parallel to a primary axis of the retention member.

The scintillating material may be formed as a plurality of opticalfibers arranged parallel to a primary axis of the retention member andextending and wherein one or more of the optical fibers extend differentlengths along the retention member. Particular embodiments may furthercomprise radiopaque markers coupled to the retention member. In certainembodiments, the radiopaque markers can be embedded in the retentionmember. In particular embodiments, the radiopaque markers are configuredparallel or perpendicular to a primary axis of the retention member.

In certain embodiments, the retention member is configured as aninflatable balloon with an external shape that conforms to a prostate ofa patient. In specific embodiments, the retention member has across-section that is generally elliptical and has a greater width thanheight and comprises an indentation along the width. In particularembodiments, the retention member comprises an insertion rod coupled toa plurality of radiopaque markers and the scintillating material. Incertain embodiments, the retention member comprises a flexible couplingmember coupled to a plurality of detectors comprising scintillatingmaterial. In certain embodiments, the retention member comprises aflexible coupling member coupled to a plurality of radiopaque markers.In particular embodiments, the retention member is configured as a rigidprobe. Certain embodiments may further comprise a plurality ofradiopaque markers and a plurality of detectors comprising scintillatingmaterial.

In particular embodiments, the scintillating material comprises awavelength shifting member. In specific embodiments, the retentionmember may be an ultrasonic probe.

Certain embodiments may also comprise a method of measuring radiationlevels in vivo. The method may comprise: providing a scintillatingmaterial, wherein the scintillating material is configured to emit lightwhen exposed to radiation; coupling the scintillating material to aretention member; securing the retention member in a specific locationin vivo; exposing the specific location and the scintillating materialto radiation; measuring the amount of light emitted from thescintillating material; and calculating the level of radiation at thespecific location based on the amount of light emitted from thescintillating material.

In certain embodiments, securing the retention member to the specificlocation in vivo comprises inflating the retention member. In particularembodiments, coupling the scintillating material to the retention membercomprises coupling the scintillating material to a cover and placing thecover over the retention member. Coupling the scintillating material tothe retention member may also comprise inserting the scintillatingmaterial into a channel of the retention member.

In particular embodiments, coupling the scintillating material to theretention member comprises wrapping the scintillating material aroundthe retention member. The scintillating material can be configured asone or more fibers, and coupling the scintillating material to theretention member may comprise arranging the or more fibers in an annularor a spiral arrangement about a primary axis of the retention member.

In particular embodiments, calculating the level of radiation at thespecific location based on the amount of light emitted from thescintillating material is performed in real time. In certainembodiments, measuring the amount of light emitted from thescintillating material comprises transferring light from thescintillating material to a photodetector via an optical coupling and afiber light guide.

Particular embodiments comprise measuring the amount of light emittedfrom the scintillating material by transferring light emitted from thescintillating material to a wavelength shifting member.

Certain embodiments comprise comparing the calculated level of radiationat the specific location to a predetermined level of radiation.Particular embodiments further comprise automatically stopping theexposure of radiation when the level of calculated level of radiation atthe specific location is equal to the predetermined level of radiation.

Certain embodiments comprise providing one or more radiopaque markerscoupled to the retention member, where the one or more radiopaquemarkers are configured to be visible when the retention member isexposed to radiation in vivo. In particular embodiments, the one or moreradiopaque markers extend parallel to a primary axis of the retentionmember. In certain embodiments, the one or more radiopaque markersextend perpendicular to a primary axis of the retention member. Inspecific embodiments, the one or more radiopaque markers are configuredto allow the longitudinal and rotational position of the retentionmember to be determined when the retention member is exposed toradiation in vivo.

The terms “a” and “an” are defined as one or more unless this disclosureexplicitly requires otherwise.

The term “approximately” and its variations are defined as being closeto as understood by one of ordinary skill in the art, and in onenon-limiting embodiment the terms are defined to be within 10%,preferably within 5%, more preferably within 1%, and most preferablywithin 0.5%.

The terms “comprise” (and any form of comprise, such as “comprises” and“comprising”), “have” (and any form of have, such as “has” and“having”), “include” (and any form of include, such as “includes” and“including”) and “contain” (and any form of contain, such as “contains”and “containing”) are open-ended linking verbs. As a result, a method ordevice that “comprises,” “has,” “includes” or “contains” one or moresteps or elements possesses those one or more steps or elements, but isnot limited to possessing only those one or more elements. Likewise, astep of a method or an element of a device that “comprises,” “has,”“includes” or “contains” one or more features possesses those one ormore features, but is not limited to possessing only those one or morefeatures. Furthermore, a device or structure that is configured in acertain way is configured in at least that way, but may also beconfigured in ways that are not listed.

The term “coupled,” as used herein, is defined as connected, althoughnot necessarily directly, and not necessarily mechanically.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein.

FIG. 1 illustrates a perspective view of an exemplary embodiment of adetector system according to the present disclosure.

FIG. 2 illustrates a perspective view of an exemplary embodiment of adetector according to the present disclosure.

FIG. 3 illustrates a side view of an exemplary embodiment of a retentionmember and a plurality of detectors, according to the presentdisclosure.

FIG. 4A illustrates a section view taken along line 4-4 of the exemplaryembodiment illustrated in FIG. 3.

FIG. 4B illustrates a section view taken along line 4-4 of the exemplaryembodiment illustrated in FIG. 3.

FIG. 5 illustrates a side view of an exemplary embodiment of a cover anda plurality of detectors, according to the present disclosure.

FIG. 6 illustrates a section view taken along line 6-6 of the exemplaryembodiment illustrated in FIG. 5.

FIG. 7 illustrates a perspective view of an exemplary embodiment of aretention member and a plurality of detectors, according to the presentdisclosure.

FIG. 8 illustrates a perspective view of an exemplary embodiment of aretention member and a plurality of detectors, according to the presentdisclosure.

FIG. 9 illustrates a perspective view of an exemplary embodiment of aretention member and a plurality of detectors, according to the presentdisclosure.

FIG. 10 illustrates a side view of an exemplary embodiment of a lockingmember and a detector, according to the present disclosure.

FIG. 11 illustrates a side view of an exemplary embodiment of a lockingmember and a detector, according to the present disclosure.

FIG. 12 illustrates a perspective view of an exemplary embodiment of alocking member and a plurality of detectors, according to the presentdisclosure.

FIG. 13 illustrates a perspective view of an exemplary embodiment of aretention member, according to the present disclosure.

FIG. 14 illustrates a perspective view of an exemplary embodiment of aretention member, according to the present disclosure.

FIG. 15A illustrates a perspective view of an exemplary embodiment of aplurality of detectors.

FIG. 15B illustrates an end view of an exemplary embodiment of aplurality of detectors.

FIG. 16A illustrates a perspective view of an exemplary embodiment of aplurality of detectors.

FIG. 16B illustrates an end view of an exemplary embodiment of aplurality of detectors.

FIG. 17A illustrates a perspective view of an exemplary embodiment of aplurality of detectors.

FIG. 17B illustrates an end view of an exemplary embodiment of aplurality of detectors.

FIG. 18 illustrates a side view of an exemplary embodiment of aretention member and a plurality of detectors and radiopaque markers,according to the present disclosure.

FIG. 19 illustrates an end view of an the exemplary embodiment of FIG.18.

FIG. 20 illustrates an end view of an exemplary embodiment of aretention member and a plurality of detectors and radiopaque markers,according to the present disclosure.

FIG. 21 illustrates an end view of an exemplary embodiment of aretention member and a plurality of detectors and radiopaque markers,according to the present disclosure.

FIG. 22 illustrates an end view of an exemplary embodiment of aretention member and a plurality of detectors and radiopaque markers,according to the present disclosure.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring initially to FIG. 1, an exemplary embodiment of a detectorsystem 50 is configured to measure in vivo and in real time the amountof radiation delivered to a specific location within a patient's body.In this exemplary embodiment, detector system 50 comprises one or moredetectors 100 configured to detect radiation, a CCD camera 60, and adata analyzer 80 (e.g., a computer) configured to analyze the radiationlevels detected by the detectors 100. Other devices may be substitutedfor the CCD camera, including a CMOS detector, photmultiplier tube (PMT)array, photodiodes and/or avalanche photodiodes (APD).

As explained in more detail below, during operation the one or moredetectors 100 may be coupled to a retention member that retains thedetectors in a desired location within a patient. The patient may thenbe exposed to radiation (e.g., as part of radiation therapy for cancer)in the location where the detectors have been placed.

Referring now to FIG. 2, a more detailed view of a detector 100illustrates the detector comprises a scintillating material 120configured to emit light when irradiated. In certain embodiments,scintillating material 120 may be relatively short (e.g. approximately1, 2, 3, 4 or 5 mm long) to measure radiation dose to a specific point.In certain embodiments, scintillating material 120 may be longer (e.g.approximately 20, 30, 40, 50, 60, 70, 80, 90 or 100 mm long) to measureradiation dose to a specific length or area. In certain embodiments,scintillating material 120 may be configured as one or morescintillating fibers. In the embodiment shown, scintillating material120 is coupled to an optical fiber light guide 130 via an opticalcoupling 140, which is in turn coupled to a photodetector 150. Duringuse, scintillating material 120 will therefore emit a light when exposedto a sufficient level of radiation. This light will be transferred fromscintillating material 120 to photodetector 150 via optical coupling 140and fiber light guide 130. Photodetector 150 (and the associated dataanalyzer) can then determine which detectors are emitting light, andconsequently, which areas have been exposed to a threshold level ofradiation.

As shown in the exemplary embodiment of FIG. 3, a plurality of detectors100 can be coupled to a retention member 70. Retention member 70 may beused to hold detectors 100 in a desired location during radiationtreatment. In specific embodiments, retention member 70 may comprise aninflatable portion so that it may be inserted into the patient whiledeflated and then inflated to increase its size when it is in thedesired location. This can allow the retention member to remain in aspecific location during radiation treatment and provide for moreaccurate detection of radiation levels.

In certain embodiments, detectors 100 may be coupled to retention member70 via channels within retention member 70. As shown in the section viewof FIG. 4A taken along line 4-4 of FIG. 3, channels 75 may be integralto retention member 70 and distributed around the circumference ofretention member 70. In this embodiment, a detector 100 can be insertedinto each channel 75 so that the radiation levels can be detected aroundthe circumference of retention member 70.

In other embodiments, detectors 100 may be coupled to retention member70 via a cover that fits over retention member 70. As shown in thesection view of FIG. 4B, detectors 100 may be inserted into channels 76of a cover 77 that may be disposed over a retention member. In certainembodiments, cover 77 and/or retention member 70 may be disposablecomponents, while detectors 100 (which are contained within channels 75or 76) are sterilized and re-used.

In still other embodiments, detectors 100 may be configured in a planararrangement in a flexible material that can be wrapped around aretention member. As shown in FIGS. 5 and 6, detectors 100 can beinserted into channels 85 of a cover 80, which may comprise a materialthat is flexible enough to be wrapped around a retention member invarious configurations. For example, as shown in FIG. 7, cover 80 may bewrapped around retention member 90 so that channels 85 (as well asdetectors 100, not visible in FIG. 7) form a spiral or helicalconfiguration along an a primary axis 95 of retention member 90. Inaddition, as shown in FIG. 8, cover 80 may be wrapped around retentionmember 90 so that channels 85 form an annular arrangement around axis 95of retention member 90. In certain embodiments, cover 80 is configuredso that it does not wrap completely around retention member 90, butinstead wraps partially around the circumference of retention member 90.

Referring now to FIG. 9, in still other embodiments a portion of thechannels 85 can be arranged to form an annular arrangement alongretention member 90, while one or more detectors are arranged orthogonalto the annular detectors 100. As shown in FIG. 9, a channel 86 isarranged orthogonal to channels 85. Channel 86 may comprise a detectorthat forms a wavelength shifting member. The detector in channel 86 canabsorb the scintillation light produced in the annular scintillatingdetectors in channels 85 and re-emits light at higher wavelengthisotropically and proportionally to the absorbed scintillation light.The wavelength shifting detector can allow a signal to be obtained fromthe several annular detectors at the same time. In this embodiment, eachannular detector is optically coupled the wavelength shifting member attheir intersection cross-section.

In exemplary embodiments, the detectors may be held in place by one of anumber of different mechanisms. For example, as shown in FIG. 10, alocking member 71 provides a pressure-based locking mechanism similar toa rubber band or o-ring. Referring now to FIG. 11, in other embodiments,a locking member 72 may utilize air pressure to hold a detector in achannel. For example, locking member 72 may comprise an inflatableelement that expands as air pressure is increased, allowing lockingmember 72 to retain the detector in the desired location within thechannel.

Referring now to FIG. 12, still other exemplary embodiments may comprisea single locking member 73 that can be used to retain multiple detectors100 in a desired location. In this embodiment, locking member 73comprises a valve mechanism 75 that can be operated to lock thedetectors in the desired location. In each of the embodimentsincorporating a locking mechanism to hold the detectors in place, thelocking mechanism should be configured so that it does not exert a forceon the detector sufficient to deform the outer surface of the detectorand potentially cause a reduction in the signal provided by thedetector.

As previously described, in certain embodiments detectors can be coupledto a cover that is used to cover a retention member. Referring now toFIG. 13, in certain embodiments the retention member may be a rectalballoon 91. In the embodiment shown in FIG. 13, rectal balloon 91 iscoupled to an inflation member 92 via a conduit 93. As known to thoseskilled in the art, rectal balloon 91 can be inflated after insertioninto the patient by repeatedly grasping and releasing inflation member92. In other embodiments a cover incorporating detectors may be placedover other types of inflatable devices, including for example, a Foleycatheter. In still other embodiments, a cover incorporating detectorsmay be placed over a retention member that is not inflatable. Forexample, such a cover may be placed over an ultrasonic probe 94, asshown in FIG. 14. In other embodiments, such a cover may be placed overenema tips or other non-inflatable devices.

The various types of retention members described above (as well as otherspecific configurations not explicitly mentioned in this disclosure) canbe used to place one or more detectors 100 in a desired location withina patient. By monitoring the response of the individual detectors duringradiation treatment, the level and area of radiation exposure may bedetermined. FIG. 15A depicts a partial side view of adjacent detectors101, 102, and 103, while FIG. 15B depicts an end view of the samedetectors. During initial stages of radiation exposure, only detector102 may be exposed to sufficient levels of radiation to cause a response(e.g., an emission of light). As shown in FIGS. 15A and 15B, adjacentdetectors 101 and 103 have not produced a response. Therefore anoperator can determine that the area proximal to detector 102 has beenexposed to a certain threshold level of radiation, while the areasproximal to detectors 101 and 103 have not been exposed to the samelevels of radiation.

As shown in FIGS. 16A and 16B, when the radiation level to the areaproximal to detector 101 (e.g., the area left of detector 102) isincreased, detector 101 will also produce a response. Similarly, asshown in FIGS. 17A and 17B, when the radiation level to the areaproximal to detector 103 (e.g., the area to the right of detector 102)is increased, detector 103 will also produce a response. By individuallytracking the responses of each detector, a user can accurately andprecisely monitor the area and levels of radiation exposure. This canallow the user to better control the radiation exposure to the patientand provide radiation to the desired areas while minimizing radiationexposure to areas in which it is not desired. For example, a detectionsystem may include a feature to automatically stop exposing the patientto radiation when certain criteria are met. In certain embodiments, theradiation exposure may be ceased when a certain number of probes detecta specific threshold of radiation levels. In other embodiments, theradiation exposure may be ceased when one or multiple probes in certainlocations detect a specific threshold of radiation level.

Furthermore, exemplary embodiments of the detection systems are capableof monitoring radiation levels in real-time, e.g. the system is capableof producing a response without a significant delay from the time thedetector is exposed to a threshold level of radiation. This can alsoallow a user to more precisely control the radiation dosage levels towhich a patient is exposed. In specific, non-limiting examples thedetection system is configured to provide a response in less than 1second. In other non-limiting examples, the detection system isconfigured to provide a response in less than 2, 3, 4, 5, 6, 7, 8, 9 or10 seconds.

Referring now to FIGS. 18-19, in certain embodiments a retention member190 may be configured as a flexible rectal or vaginal dilator. Inspecific embodiments, retention member 190 may be a rectal or vaginaldilator comprised of silicone. In the embodiment shown, a plurality ofradiopaque markers 105 may be coupled (e.g., embedded) to retentionmember 190. Radiopaque markers 105 are opaque to radiation and aretherefore visible during radiation treatment (e.g., when retentionmember 190 is inserted in vivo and the area proximal to retention member190 is exposed to radiation). In specific embodiments, radiopaquemarkers 105 may be arranged so that they extend along the primary orlongitudinal axis 195 of retention member 190 and to a distal end 199 asshown in FIG. 18. In addition, radiopaque markers 105 may be configuredso that they are perpendicular to longitudinal axis 195 of retentionmember 190 as shown in FIG. 19. In certain embodiments, radiopaquemarkers 105 are arranged asymmetrically to allow the rotational positionof retention member 190 to be determined. Radiopaque markers 105 cantherefore allow the longitudinal and rotational position of retentionmember 199 to be determined during and after insertion into a patient.

In addition to radiopaque markers 105, retention member 190 alsocomprises a plurality of detectors 200 configured to detect radiation.In specific embodiments, detectors 200 comprise a scintillating materialconfigured to emit light when irradiated. In certain embodiments,detectors 200 may be configured as one or more scintillating fibers. Asshown in FIG. 18, detectors 200 may extend to different lengths alongretention member 190. For example, detectors 200 may be arrangedgenerally parallel to longitudinal axis 195 and terminate at differentdistances from distal end 199 of retention member 190. This arrangementcan allow the dosage level to be determined at various locations alongretention member 190.

Referring now to FIG. 20, a retention member 290 may be configured as aninflatable rectal balloon whose shape conforms to the prostate. Inspecific embodiments, retention member 290 may be configured as having across-section that is generally elliptical and has a greater width thanheight (when viewed in the position shown in FIG. 20) and includes anindentation 291 located along the wider portion of retention member 290.In certain embodiments, retention member 290 may comprise an insertionrod 293 coupled to a plurality of radiopaque markers 205 and a pluralityof detectors 300 (including, for example, detectors comprisingscintillating material). Similar to previously-described embodiments,the spatial relationship between radiopaque markers 205, detectors 300,and features (e.g., an end) of retention member 290 are known prior toinsertion into a patient. This allows a user to determine the locationof retention member 290 and the level of radiation dosage provided to apatient after retention member 290 has been inserted into a patient'srectum and the region proximal to the prostate has been exposed toradiation.

Scintillating fibers with radiopaque markers are attached to theinsertion rod within the balloon. The radiopaque markers are placed at aknown distance from the scintillating fiber tip and are used to localizethe position of the detector. The scintillating fibers are placed atvarious heights along the insertion rod.

Referring now to FIG. 21, a retention member 390 may be configured as aninflatable rectal balloon with an insertion rod 393. In this exemplaryembodiment, retention member 390 comprises a plurality of radiopaquemarkers 305 and detectors 400 that function generally equivalent tothose in previously-described embodiments. In this embodiment, retentionmember 390 comprises a flexible coupling member 310 that extends acrossretention member 390 and is coupled to radiopaque markers 305 anddetectors 400.

In exemplary embodiments, flexible coupling member 310 can expand orcontract as the diameter of retention member 390 is altered. Forexample, retention member 390 may be deflated prior to insertion withina patient, and insertion rod 393 can be used to insert retention member390 into the patient's rectum. When retention member 390 is located inthe desired position, retention member 390 can be expanded (e.g.,inflated) so that the outer diameter of retention member 390 isincreased. As the diameter of retention member 390 is increased,flexible coupling member 310 expands and increases the distance betweenindividual radiopaque markers 305 and detectors 400.

Referring now to FIG. 22, a retention member 490 is configured as arigid rectal probe. In this embodiments, a plurality of radiopaquemakers 405 and detectors 500 are located within retention member 490. Inthe exemplary embodiment shown, detectors 500 are configured as aclosely packed unit within retention member 490. In certain embodiments,retention member 490 may comprise approximately 10, 15, 20, 25, 30, 35,40, 45 or 50 detectors 500.

All of the apparatus and/or methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the apparatus and methods of this invention have beendescribed in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to theapparatus and/or methods and in the steps or in the sequence of steps ofthe method described herein without departing from the concept, spiritand scope of the invention.

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

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The invention claimed is:
 1. A method of measuring radiation levels inreal time during radiation therapy of a prostate, the method comprising:(a) inserting a rectal balloon into a rectum of a male patient havingprostate cancer; (i) said rectal balloon having an external shape thatconforms to a prostate, wherein said rectal balloon has a cross-sectionthat is generally elliptical having a greater width than height whenviewed from a first end of said rectal balloon, and wherein said rectalballoon has an indentation along its width; (ii) said rectal ballooncoupled to a dosimeter comprising a plastic scintillating materialcoupled to an optical guide; (iii) said indentation of said rectalballoon extending axially from the first end of said rectal balloon; and(iv) said indentation extending inward toward said dosimeter; (b)inflating said rectal balloon; (c) coupling said dosimeter to aphotodetector coupled to a data analyzer; (d) initiating a radiationtherapy of said prostate; (e) calculating a level of radiation at saidprostate based on the amount of light detected by said photodetector;and (f) stopping said radiation therapy when said calculated level ofradiation is equal to a predetermined level of radiation.
 2. The methodof claim 1, wherein said balloon comprises a channel and said dosimeteris inside said channel.
 3. The method of claim 2, wherein said rectalballoon comprises one or more radiopaque markers, the method furthercomprising: (a) visualizing said one or more radiopaque markers; and (b)positioning said rectal balloon based on said visualization so that saidrectal balloon is in a desired location.
 4. The method of claim 2,wherein said rectal balloon comprises radiopaque markers asymmetricallyarranged on said rectal balloon, the method further comprising: (a)determining the position of said radiopaque markers; and (b) positioningsaid rectal balloon until said rectal balloon is in a desired locationbased on said position of said radiopaque markers.
 5. The method ofclaim 1 wherein said radiation therapy is radiation beam therapy.
 6. Themethod of claim 1, wherein said rectal balloon comprises one or moreradiopaque markers, the method further comprising: (a) visualizing saidone or more radiopaque markers; and (b) positioning said rectal balloonbased on said visualization so that said rectal balloon is in a desiredlocation.
 7. A device for in vivo real time dosimetry during radiationtherapy, said device comprising: (a) an inflatable rectal balloonfluidly coupled to a conduit for inflating said balloon; (b) saidballoon having an external shape that conforms to a prostate, whereinsaid rectal balloon has a cross-section that is generally ellipticalhaving a greater width than height when viewed from a first end of saidrectal balloon, and has an indentation along its width; (c) said rectalballoon comprising a channel thereon, said channel containing a realtime dosimeter; (d) said indentation of said rectal balloon extendingaxially from the first end of said rectal balloon; and (e) saidindentation extending inward toward the real time dosimeter; (f) saidreal time dosimeter comprising a water equivalent plastic scintillatorcoupled to an optical fiber; and (g) wherein said real time dosimetercan monitor an in vivo dose of radiotherapy beams or brachytherapy inreal time.
 8. The rectal balloon of claim 7, said rectal balloon furthercomprising an indentation when inflated to conform said rectal balloonto a prostate when in use.
 9. The rectal balloon of claim 7, whereinsaid real-time dosimeter comprises a plurality of plastic scintillatorsoptically coupled to a plurality of optical fibers and wherein one ormore of the optical fibers extend different lengths along said rectalballoon.
 10. The rectal balloon of claim 7, wherein a plurality ofchannels contain a plurality of real-time dosimeters.
 11. The rectalballoon of claim 7, further comprising one or more radiopaque markers onsaid rectal balloon.
 12. The rectal balloon of claim 7, furthercomprising one or more radiopaque markers arranged asymmetrically onsaid rectal balloon.
 13. The rectal balloon of claim 7, wherein saidreal time dosimeter is configured to be coupled to a photodetector.